Rework and simplify RCU code #1533

Job	Run time
run-checker (enable-asan enable-ubsan no-shared no-asm -DOPENSSL_SMALL_FOOTPRINT -fno-sanitize=fu...	9m 53s
run-checker (no-ct)	5m 23s
run-checker (no-dso)	5m 11s
run-checker (no-dynamic-engine)	5m 8s
run-checker (no-ec2m)	5m 8s
run-checker (no-engine no-shared)	4m 17s
run-checker (no-err)	5m 35s
run-checker (no-filenames)	5m 22s
run-checker (enable-ubsan no-asm -DOPENSSL_SMALL_FOOTPRINT -fno-sanitize=function)	8m 34s
run-checker (no-module)	5m 8s
run-checker (no-ocsp)	5m 14s
run-checker (no-pinshared)	5m 22s
run-checker (no-srp)	5m 19s
run-checker (no-srtp)	5m 30s
run-checker (no-ts)	5m 12s
run-checker (enable-weak-ssl-ciphers)	5m 24s
run-checker (enable-zlib)	5m 26s
	1h 37m 6s

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